Question

4. Life cycles: Interpret the life cycles using the terms you have learned in class (5pts each; 10pts). B 10 Serratella sp. LENGTH CLASS WAS 4. Reference the figure above where length class is the length in millimeters for this mayfly, Serratello sp. in a permanent, third-order Appalachian stream (data from Huryn and Wallace 1987) Dashed lines indicate adults and first letter of the month begins with July, August, etc. on the x axis. 4. First, describe the lifecycle using terms we discussed in class (e.g. duration number of cohorts, and seasonal vs non-seasonal) and then describe the possible ways the species could respond to a 2°C temperature increase in autumn (October-December

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Nymph

Immature mayflies are aquatic and are referred to as nymphs or naiads. In contrast to their short lives as adults, they may live for several years in the water. They have an elongated, cylindrical or somewhat flattened body that passes through a number of instars (stages), molting and increasing in size each time. When ready to emerge from the water, nymphs vary in length, depending on species, from 3 to 30 mm (0.12 to 1.18 in). The head has a tough outer covering of sclerotin, often with various hard ridges and projections; it points either forwards or downwards, with the mouth at the front. There are two large compound eyes, three ocelli (simple eyes) and a pair of antennae of variable lengths, set between or in front of the eyes. The mouthparts are designed for chewing and consist of a flap-like labrum, a pair of strong mandibles, a pair of maxillae, a membranous hypopharynx and a labium

Subimago

The final moult of the nymph is not to the full adult form, but to a winged stage called a subimago that physically resembles the adult, but which is usually sexually immature and duller in colour. The subimago, or dun,[6] often has partially cloudy wings fringed with minute hairs known as microtrichia; its eyes, legs and genitalia are not fully developed. Females of some mayflies lack a subimago state but the adult stage appears like a subimago with microtrichia on the wing membrane. Oligoneuriine mayflies form another exception in retaining microtrichia on their wings but not on their bodies.[7] Subimagos are generally poor fliers, and typically lack the colour patterns used to attract mates. After a period, usually lasting one or two days but in some species only a few minutes, the subimago moults to the full adult form, making mayflies the only insects where a winged form undergoes a further moult.

Imago
Adult mayflies, or images, are relatively primitive in structure, exhibiting traits that were probably present in the first flying insects. These include long tails and wings that do not fold flat over the abdomen.[8] Mayflies are delicate-looking insects with one or two pairs of membranous, triangular wings, which are extensively covered with veins. At rest, the wings are held upright, like those of a butterfly. The hind wings are much smaller than the forewings and may be vestigial or absent. The second segment of the thorax, which bears the forewings, is enlarged to hold the main flight muscles. Adults have short, flexible antennae, large compound eyes, three ocelli and non-functional mouthparts. In most species, the males' eyes are large and the front legs unusually long, for use in locating and grasping females during the mid-air mating. In the males of some families, there are two large cylindrical "turban" eyes that face upwards in addition to the lateral eyes.[9] They are capable of detecting ultraviolet light and are thought to be used during courtship to detect females flying above them.[10] In some species, all the legs are functionless, apart from the front pair in males. The abdomen is long and roughly cylindrical, with ten segments and two or three long cerci (tail-like appendages) at the tip. Uniquely among insects, mayflies possess paired genitalia, with the male having two aedeagi (penis-like organs) and the female two gonopores (sexual openings).

In spring, water temperature needs to be in the low 40s. Peak hatches occur when the water temps hit 46 degrees and up. In summer, especially evenings, water temp needs to be in the 60-degree minimum. For fall mayflies, peak hatches will happen when the water temp is over 46 degrees. At 2 degrees increase in autumn, the eggs remain dormant or won't hatch

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